I think the A8 has less of an enthusiast fllowing than the A3's and A4's...
I was also looking at these recently as an alternative option for upgrading from my A4 (I want somehting with a bit more space in the back for long cruises out for familly holidays):
I assume you're after the 2003-2010 model? (
Parkers' Info)
Of the options: 3.0, 4.0 and 4.2 TDI....
The 4.0TDI is the older engine: the 4.2TDI is better economy (28mpg vs 30mpg) + power (270bhp vs 321bhp!), so that's the one to go for if you want the V8.
Things to bear in mind: it's about 120kg heavier than the 3.0TDI and after March 2006, you will get STUNG on the UK road tax for the 4.2TDI (over £460pa?).... but then you do lose nearly 2 seconds on the 0-62mph time if you get a 3.0 rather than a 4.2!! (7.6sec vs 5.7sec).
In the grand scheme of things, a 321bhp 4.2 V8 that gets 33mpg is fantastic value even if you do pay more than £200pa extra in tax... and also bear in mind that the V8 TDI tends to come fully loaded, while the 3.0TDI's aren't as likely to have ALL the toys...
There are a LOT more SE's out there than Sport models... so you get more choice. Not driven them back to back, so not sure which is preferred.
I'm interested to hear why you didn't like the adjustable air suspension?